Polymer composites referred to as nanocomposites have conventionally been prepared by compounding an organic polymer such as polyamide, polystyrene, polypropylene, polyimide or polyurethane with clay. Since the resulting polymer composite is finely dispersed in a clay layer having a large aspect ratio, the elastic modulus, heat deflection temperature, gas permeability, burning rate and so forth are known to be effectively improved.
An organic/inorganic composite hydrogel having a three-dimensional mesh structure composed of a polymer of a water-soluble acrylic monomer and a water-swellable clay mineral has been disclosed as an example of a nanocomposite material having particularly superior mechanical properties (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-053762 and Japanese Unexamined Patent Application, First Publication No. 2004-143212). Since this organic/inorganic composite hydrogel has superior mechanical properties not found in other gels, it is expected to be applied in various applications. In order to deploy the application thereof in various applications, the organic/inorganic composite hydrogel is frequently required to be formed into a coated film such as a thin film or film, formed into a pattern, or formed into a laminated structure, and in such cases, the composite hydrogel is easily molded into these shapes and forms by producing an organic/inorganic composite hydrogel using an energy beam.
As an example of a production process of the prior art, a process has been disclosed in which an acrylamide or acrylamide derivative and a (meth)acrylic acid ester and so forth are polymerized by heating or irradiation with ultraviolet light in the presence of a water-swellable clay mineral in an aqueous medium and an aqueous polymerization initiator (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-053762 and Japanese Unexamined Patent Application, First Publication No. 2004-143212). However, in the case of using a water-soluble peroxide for the polymerization initiator and carrying out the polymerization reaction by irradiating with ultraviolet light as in the process disclosed here, there were cases in which the mechanical properties of the resulting organic/inorganic composite hydrogel were not adequately obtained as well as cases in which elution of linear polymer occurred. In addition, since a water-soluble peroxide is used for the polymerization initiator, since the polymer composite is polymerized by allowing to stand undisturbed for several tens of minutes to more than ten hours at a constant temperature such as room temperature in the state in which oxygen in the polymer solution has been removed, there has been a need to simplify the production process as well as shorten the production time.
These problems occur particularly prominently when forming a coated film, thereby preventing the obtaining of an organic/inorganic composite hydrogel coated film having adequate mechanical properties and resulting in a desire to realize an organic/inorganic composite hydrogel coated film suitable for deployment in various applications.